Edit: obligatory explanation (thanks mods for squaring me away)…
What you see via the UI isn’t “all that exists”. Unlike Reddit, where everything is a black box, there are a lot more eyeballs who can see “under the hood”. Any instance admin, proper or rogue, gets a ton of information that users won’t normally see. The attached example demonstrates that while users will only see upvote/downvote tallies, admins can see who actually performed those actions.
Edit: To clarify, not just YOUR instance admin gets this info. This is ANY instance admin across the Fediverse.
every website logs ip. The question is whether the admin maintains those logs. However a web server needs your IP so they can route traffic back to you. That IP gets logged so that if something is not working the admin can review the logs and figure out what is going on. Many websites that are privacy focused either turn the logging off or dump the logs fairly quickly. Doing something like that means the admin needs to take steps to create other avenues for troubleshooting that don’t factor user data into the scenario. With smaller projects like instances hosted on lemmy that might not always be feasible for volunteer admins. This doesn’t necessarily mean they are doing anything wrong. Lots of websites maintain logs that include IP addresses.